Wire carriers for oil well perforators



Nov. 1, 1966 w. T. BELL ETAL 3,282,213

WIRE CARRIERS FOR OIL WELL PERFORATORS Filed July 1, 1964 INVENTORSI WILLIAM T. BELL, WINTON B. BLAIR 8 BYROBERT M. SHAPIRO their ATTORNEYS 3,282,213 WIRE CARRIERS FQR 01L i VELL PERFQRATGRS William T. Bell, Winton l5. Blair, and Robert M, Shapiro,

Houston, Tex., assignors to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed July 1, 1964, Ser. No. 379,513 12 Claims. (til. 102-2ti) This invention relates to well perforating apparatus; and, more particularly, to a novel and improved carrier for oil well perforating apparatus of the type employing shaped explosive charge devices.

An important step in completing an oil well having a casing cemented in place is to create perforations through the casing and cement around it which extend into the surrounding earth formations. One widely used method of perforating a well is to lower a plurality of shaped explosive charge devices to levels in the well where oil bearing strata have been found. The shaped charge devices, which are supported at predetermined longitudinal spacing on a suitable carrier and are oriented in predetermined angular positions, are then detonated to produce the perforations which extend through the metal well casing and the surrounding cement and into the oilbearing formation.

An important part of shaped charge Well perforating apparatus is the carrier. The carrier must be strong enough and rigid enough to support the charge devices and maintain them in their proper alignments; but,'at

the same time, it should not be undesirably stiff or rigid, inasmuch as it may often have to bend in order to pass through crooked places in the well. It should be constructed so as to be readily assembled, and should preferably employ standardized interchangeable parts which can be assembled in various configurations, depending upon the diameter of the well and the number, size and spacing of the charge devices.

A particularly desirable feature is that upon detonation of the charges the carrier will not fracture or break up in such a way that pieces are separated and remain in the well, thus creating a danger of blocking it and preventing other operations from belng performed. In other Words, the carrier should be completely recoverable.

Another requirement for well perforating apparatus is that it be small enough to be accommodated within very small diameter tubing, say as small as two inches or less in internal diameter. When it is considered that shaped charge devices for small Wells may be only slightly smaller than the well, there are very close practical limits on the size of a carrier for them.

A number of different types of carriers have been previously suggested for meeting one or more of the above and other requirements, but nearly all of them have sacrificed one or more significant characteristics to enable the enhancement of other characteristics. Thus, known forms of well perforatin apparatus have one or more limitations which, while not disadvantageous for many purposes, nevertheless restrict their use for some specific purposes. Therefore, a user may have to stock a number of different types of carriers and charge devices to meet various needs.

An object of the present invention is to provide a well perforating apparatus having a carrier which is compact in size and utilizes standardized parts, thereby permitting it to be employed in wells of nearly all sizes, particularly those of small diameter, without substantial modification.

Another object is to provide a carrier which is completely recoverable from the well after detonation of the shaped charge devices.

A further object of the invention is to provide a 3,282,213 Patented Nov. 1, 19%5 "ice carrier which is suthciently strong to enable a large number of shaped charge devices to be carried thereon and which enables positioning varying numbers of devices at varying spacings.

Yet another object is to provide a carrier for encapsulated shaped explosive charge devices for well perforating which can readily be assembled with very simple equipment.

These and other objects of the invention are accomplished by providing novel and improved carriers for well perforating apparatus comprising a pair of elongated ribbon-like wire members, each having, in crosssection, a major axis and a minor axis. When assembled as a carrier, the members are spaced on either side of a central axis with the major axis of the members and the central axis or" the assembly lying in a longitudinally extending plane. The wire members include alternately occurring inwardly pointing curved portions and outwardly pointing curved portions, which are respectively, opposed to each other.

The wire members are adapted to receive encapsulated shaped explosive charge devices having correspondingly positioned curved attaching means with the outwardly pointing curved portions of the members having curvatures complementary to those of the attaching means and receivable therein. Means are provided for securing the wire members relative to one another at spaced-apart locations along their length, such means preferably being a plurality of wire clips, each of which is preattached to one of the wire members and has a free end which is hooked around the other wire member after the shaped charge devices are assembled therein.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a front elevational view of a Well perforating device utilizing a typical carrier according to the present invention, in place in a well;

FIG. 2 is a side elevational view of the device illustrated in FIG. 1;

FIG. 3 is an enlarged view, taken in section along the line 3-3 of FIG. 2 and looking in the direction of the arrows, and the shaped charge device being shown in full view rather than in section for simplicity; and

FIG. 4 is a fragmentary front elevational view of the apparatus of FIG. 1 on an enlarged scale.

Referring to FIGS. 1 and 2, a representative well perforating apparatus, illustrated in place in a well having a metal casing 10 held in place with cement 12, is supported in the well by a cable 14, which includes loadsupporting cable elements and electrical conductors connected to an electrically initiated detonator 16. Fastened to the lower end of the detonator 16 is a generally semi-circular support plate 18 having a circular hole 20 therein. The hole 20 receives a cylindrical mounting piece 22 having generally semi-cylindrical laterally extending bosses 24- thereon to which a plate 26 carrying a spacer bar 28 is bolted. The spacer bar 28 maintains the upper end of the perforating apparatus centered in the casing 10. Bolted onto the lower end of the plate 26 is an upper bracket 30 (one plate of which is broken away in FIG. 1) which will be described in greater detail hereinafter.

A carrier 32 suspended from the bracket 30 comprises a pair of spaced-apart, ribbon-like wire members 34 and 36. The members 34 and 36, as best seen in FIG. 3, are generally rectangular in cross-section with the flat longer sides being parallel to the major axis and the generally rounded shorter edges being at the ends of the major axis. It has been found that the dimension along the major axis must be at least about 1.75 times greater than the dimension along the minor axis. It is preferred, however, that this major dimension be about twice that of the minor dimension.

As shown in FIG. 4, each of the members 34 and 36 comprises alternately occurring, reversedly curved portions 34a, 36a, and 34b, 36b interconnected by straight portions 340, 36c, the members 34 and 36 being identical but disposed on the carrier 32 in opposed relations; that is, one member 34 is oriented, in elevation, in laterally reversed position relative to the other member 36.

More particularly, the wire members 34 and 36 are disposed relative to each other on opposite sides of the central axis of the carrier 32 in such a way that the curved portions 34a and 36a point inwardly and are closely spaced. The curved portions 345 and 36b point outwardly and are widely spaced apart so that they cooperatively accommodate an encapsulated shaped explosive charge device 40. As shown'in FIG. 4, the members 34 and 36 are held against the opposite sides of the charge 40 by clips 38 consisting of short pieces of wire which are preferably prefastened to the curved portions 34a of one wire member 34 by wrapping one end 380: two or three times around the member. The free end 38b of the clip 38 crosses to the other wire member 36 and extends partially around the outer edge of that member.

The wire clips 38 interconnect the spaced-apart wire members 34 and 36 of the carrier 32 and are arranged to release the members from their original spacing upon detonation of the charges 40; that is, the hook portions 381: tend to open upon detonation, permitting the wire members to be separated outwardly. Thus, the members 34 and 36 do not rigidly resist the laterally directed energy of the explosive but are moved outwardly thereby enabling the members to remain intact. A further advantage of the clip connectors 38 is that they remain attached to one of the wire members after detonation and are therefore recovered along with the wire members when the used carrier 32 is withdrawn from the well.

Contrary to conventional engineering practices which would dictate that where a given material fails in a par ticular service, a stronger, harder material must be used, it has been found instead that a material having a lower static strength will withstand the dynamic explosive forces where a material of much greater static strength will fail.

Accordingly, it has been found that the wire members 34 and 36 must be of a metal which, when subjected to the severe dynamic shock of the exploding shaped charge devices, has sufiicient strength and tenacity to withstand severe dynamic shocks as well as possessing a low notch sensitivity and low rate of crack propagation.

Such metals, therefore, have a low hardness, a high impact strength and are reasonably free of harmful inclusions. Thus, it has been found that the wire members 34 and 36 are preferably made of a relatively ductile and malleable material such as a steel having a Rockwell B hardness of between about 80 to 95 and a carbon content of no more than about 0.35 percent. Such requirements are well suited by employing an A.I.S.I. 1018 steel. I

Accordingly, because they are made of a relatively ductile and malleable steel and because of their geometric shape in cross-section, the members 34 and 36 of the present invention are capable of sustaining the detonation of the charges 40 they carry without fracture, and the carrier 32 can be recovered intact from the well after use. As a result of charge detonation, a significant amount of erosion or pitting as well as compression occurs in the curved portions of the members 34 and 36 where the shaped charge devices 40 are supported. Inasmuch as the material is relatively ductile and soft and has a correspondingly high toughness, however, the explosive energy impinging on the members 34 and 36 is absorbed without producing fracture and subsequent bending is possible without causing breakage despite the erosion and pitting.

Another important advantage of the present invention is that the wire members 34 and 36 are relatively small in cross-section, for example about one eighth inch by one quarter inch. 'Accordingly, the apparatus is readily accommodated in very small diameter wells such as two inches or less even with charges which have a diameter of 1.4 inches, for example.

As shown in FIG. 3, the case of the shaped charge de vice 40 is formed with oppositely disposed, outwardly extending bosses 42 and 44 and a circumferential flange 46. Only one side of the charge device 49 is shown in FIG. 3, but it will be understood that the opposite side is shaped in the same manner. The bosses 42 and 44 refine a first groove 43 for receiving a. curved portion 34b of the wire member 34 and a second groove 58, defined between the boss 46 and the flange 44 and located forward of the groove 48, may, alternatively, receive the portion 34]). Thus, the shaped charge devices 40 can be mounted on the carrier 32 in either of two positions, and the distance at which the shaped charge devices 46 are mounted from the wall of the well can be varied. The preferred types of shaped charge devices 43 are those having frangible cases which disintegrate upon detonation of the explosive charges therein. Thus, no large pieces of the cases are left to block the well.

Referring again to FIGS. 1 and 2, the upper bracket 30 supporting the carrier Wire members 34 and 36 comprises a substantially flat plate 60, which is bolted at its upper end to the spacer arm plate 26, and a clamp plate 62..

The clamp plate 62, as best illustrated in FIG. 1, is formed with two grooves 64 and 66 which are shaped to receive the ends of the wire members, the ends including segments comprising two outwardly pointing portions 34!) and 36b and the adjacent straight portions 34c and 36c on each side thereof. In FIG. .1, the plate 62, which is fastened by two bolts to the plate 643, has been cut away along a plane passing through the near sides of the wire members to more clearly illustrate the bracket structure. To ensure that the wire members 34 and 36 are firmly clamped in place between the brackets, it is preferable to form the grooves 64 and 66 to a depth less than the thickness of the wire members, so that the clamp plate 62. can be drawn tightly against the wire members by the bolts.

Connected to the lower ends of the carrier wire member 34 and 36 by a bracket 72 is a plate '74 carrying a weight76 and a spacer bar 73. To facilitate passage of the carrier 32 through crooked parts of the well, the lower bracket 72. is, preferably, arranged to permit longitudinal movement of each of the wire members 34 and 36 relative to the other. To this end, the bracket 72 consists of a flat plate 80, to which plate 74 is bolted, and a plate 82 formed with bosses 84, 85 and 86, which engage the upwardly facing edges of two adjacent straight portions 340 and 360 of the wire members 34 and 36. It will "be noted that the lower edges are unrestrained, and therefore, one wire member 34 may move downwardly relatively to the other member 36 when the carrier 32 is bent in the plane of FIG. 1. The bosses 84, 85 and 86 of the lower bracket plate 82 have a height slightly greater than the thickness of the Wire members 34 and 36, so that the bracket plate 82 when bolted to the plate 84 does not clamp the wire members.

As shown in FIGS. 1 and 2, a plurality of shaped charge devices 49, each mounted between the wire members 34 and 36 in the manner shown in FIG. 4, is coupled to a detonating cord 90. The cord 93, leading from the detonator 16, is threaded through the spacer ring 23 and is held in place in a notched boss 92 (FIG. 3) at the rear of each of the charge devices 40 which, in the embodiment illustrated in the drawings, are installed 1! Point in alternately opposite directions. The cord 90, therefore, passes from one side of the plane of the wire members 34 and 36 to the other side. Alternatively, of course, the shaped charges 4t) may all be oriented in the same direction, in which case, the cord 0 can be passed in front of each of the clips 38 and then back behind each charge device.

To assemble the perforating device, the shaped charge devices 40 are placed between the wire members 34 and 36 and a suitable hand tool used to bend the free end portions 33b of the clips 33 around the wire member 36. The detonating cord 99 is then laced through the clips 38 and inserted into the notched bosses 92 on the charge devices 40. It will be apparent that the assembly procedure is simple enough so that it can readily be ac? complished at the well site, if desired.

in use, when the perforating apparatus has been lowered to the proper elevation in the well and oriented, the

' shaped explosive charge devices 40 are detonated. Upon detonation, the frangible casings of the devices 40 disintegrate and particles of the charge casings impinge with high energy upon the relatively narrow inner edges of the wire members 34 and 36, especially in the regions of the inwardly facing curved portions 34b and 36b, thereby producing noticeable erosion and pitting of the inner edge of those regions. In conventional carriers made of wire members are relatively brittle materials, the eroded or pitted portions of the wire members adjacent tothe charge devices would be notched so that, when the carrier wa withdrawn from the well, the repeated flexing or bending of the wire members would tend to induce fracture thus leaving broken-off pieces of the wire members in the well. On the other hand, since the members 34 and 36 of the present invention are made of relatively ductible malleable materials, and particularly a steel having a Rockwell B scale hardness of between about 80 and 95 and a carbon content of no more than about 0.35 percent, they have very low notch sensitivity and can be bent and twisted repeatedly without fracture as the carrier 32 is withdrawn from the well.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a retrievable carrier for holding explosive charges in a well perforating apparatus, an undulating wire memher having, in a cross-sectional plane perpendicular to the longitudinal axis of said wire member, a major transverse axis in the plane of its undulation and a minor transverse axis and adapted in conjunction with another similar wire member having opposed undulations to carry a plurality of explosive charge devices between the opposed undulations thereof and to resist fracture upon detonation of the charges.

2. A carrier according to claim 1 in which the dimension of the wire member in the direction of the major transverse axis is at least about 1.75 times greater than the dimension thereof in the direction of the minor transverse axis.

3. A carrier according to claim 1 wherein said wire member is rounded at the ends of said major axis.

4. A carrier according to claim 1- in which the wire member is made of a steel having a hardness in the range of from about to about on the Rockwell B scale and a carbon content of no more than about 0.35 percent. 5. A retrievable carrier for holding explosive charges in well perforating apparatus comprising a pair of wire members having opposed lateral undulations in the same plane and each having, in a cross-sectional plane perpendicular to the longitudinal axis of said wire member, a major transverse axis in the plane of the undulations and a minor transverse axis, and means for holding said pair of wire members in generally parallel spaced relation to carry a plurality of explosive charge devices between the opposed undulations thereof and to avoid fracture of the members upon detonation of the charges.

6. A retrievable carrier according to claim 5 wherein said holding means comprises clamp means at one end,

.and restraining bracket means at the other end facilitating relative longitudinal motion of the wire members.

7. A carrier according to claim 5 in which the dimension of the wire member in the direction of the major transverse axis is at least about 1.75 times greater than the dimension thereof in the direction of the minor transverse axis. p

8. A carrier according to claim 5 wherein said wire member is rounded at the ends of said major axis.

9. A carrier according to claim 5 in which the wire member is made of a steel having a hardness in the range of from about 80 to about 95 on the Rockwell B scale and a carbon content of no more than about 0.35 percent.

10. A retrievable carrier according to claim 5 wherein said holding means includes wire clip means disposed at spaced intervals for holding said wire members together.

11. A carrier according to claim 10 wherein said wire clip means has one end encircling a portion of one of said wire members and another end partially encircling the other of said wire members.

12. Well perforating apparatus comprising a pair of elongated ribbon-like wire members, each having, in a cross-sectional plane perpendicular to the longitudinal axis of said wire member, a major axis and a minor axis said members being spaced on either side of a longitudinal central axis, the edges of said wire members parallel to the major axis being generally flat and the edges at the ends of said major axis being generally convexly curved, said major axis and central axis lying in a longitudinally extending plane, and said wire members having alternately occurring inwardly pointing curved portions and outwardly pointing curved portions, a plurality of encapsulated shaped explosive charge devices having diametrically positioned attaching means thereon, said shaped charge devices and outwardly pointing curved portions having complementary curvatures, said outwardly pointing curved portions received in said attaching means, and means for securing said wire members together and releasing upon detonation of the charges.

References Cited by the Examiner UNITED STATES PATENTS 2/1953 Sweetman l0220 7/1961 Toelke 10'22O 

1. IN A RETRIEVABLE CARRIER FOR HOLDING EXPLOSIVE CHARGES IN A WELL PERFORATING APPARATUS, AN INDULATING WIRE MEMBER HAVING, IN A CROSS-SECTIONAL PLANE PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAID WIRE MEMBER, A MAJOR TRANSVERSE AXIS IN THE PLANE OF ITS UNDULATION AND A MINOR TRANSVERSE AXIS AND ADAPTED IN CONJUNCTION WITH ANOTHER SIMILAR WIRE MEMBER HAVING OPPOSED UNDULATIONS TO CARRY A PLURALITY OF EXPLOSIVE CHARGE DEVICES BETWEEN THE OPPOSED UNDULATIONS THEREOF AND TO RESIST FRACTURE UPON DETONATION OF THE CHARGES. 